This invention relates to copolyformals and more particularly to copolyformals containing carborane and polynitroalkyl groups.
Previously, carborane based burning rate modifiers have been incorporated in propellant compositions as separate species, physically dissolved in the binder. This has permitted crystallization and migration of the burning rate modifier within the propellant composition and across interfaces with adjoining materials, resulting in nonuniform distribution of the carborane compound within the propellant compositions.
U.S. Pat. No. 3,258,479 discloses the polymerization of 1,2-bis(2-hydroxyethyl)-1,2-dicarbadodecaborane(12), B.sub.10 H.sub.10 [C(CH.sub.2 CH.sub.2 OH)].sub.2, with either (a) 1,2-bis(carboxymethyl)-1,2-dicarbadodecaborane(12), B.sub.10 H.sub.10 [C(CH.sub.2 COOH].sub.2, or (b) the corresponding acid chloride B.sub.10 H.sub.10 [C(CH.sub.2 COCl)].sub.2 to form a polyester which is useful in solid rocket propellants. U.S. Pat. No. 3,311,593 discloses the reaction of 1,2-bis(hydroxyethyl)-1,2-dicarbadodecaborane(12) diisocyanate of the formula B.sub.10 H.sub.10 [C(N.dbd.C.dbd.O)].sub.2 to produce a polyurethane which is useful in solid rocket propellants. Because of their physical properties these polymers are not suitable as binders for many solid propellant applications. Moreover, the dicarborane content of these polymers is fixed and can not be tailored to a variety of applications.
It would be desirable in polynitroalkyl propellant binders to tie down the carborane based burning rate modifiers in a uniform distribution and thus achieve a more uniform burning propellant. It would also be desirable to vary the carborane content of propellant binders in controlled amounts.